Absorption of scintillation light in a 100 l liquid xenon -ray detector and expected detector performance

An 800 l liquid xenon scintillation γ -ray detector is being developed for the MEG experiment which will search for μ + → e + γ decay at the Paul Scherrer Institut. Absorption of scintillation light of xenon by impurities might possibly limit the performance of such a detector. We used a 100 l prototype with an active volume of 372 × 372 × 496 mm 3 to study the scintillation light absorption. We have developed a method to evaluate the light absorption, separately from elastic scattering of light, by measuring cosmic rays and α sources. By using a suitable purification technique, an absorption length longer than 100 cm has been achieved. The effects of the light absorption on the energy resolution are estimated by Monte Carlo simulation.